The present invention relates to an image forming apparatus having a photosensitive drum, and more specifically to an image forming apparatus having a photosensitive drum with a relatively small diameter.
Recently small-sized information apparatuses have been developed which can be placed on a desk for personal use. To miniaturize the apparatuses, the packing density of circuits is increased and component accuracy improved. Miniaturization is also required of image forming apparatuses such as facsimiles and copying machines. Among the image forming apparatuses, those apparatuses which have an image carrier (hereinafter referred to as a photosensitive drum) rotating in the center of the apparatus housing must be designed so that the diameter of the photosensitive drum is reduced for compactness. Accordingly, process units, such as a charger, developing device, transfer device, cleaning unit, discharger, etc., arranged around the photosensitive drum, must also be reduced in size.
Thus, in the image forming apparatuses of this type, the process units surrounding the photosensitive drum are limited in size as the diameter of the photosensitive drum is reduced from 100 mm to 80 mm, for example. In this operation, it is expressly advisable to provide, e.g., pretransfer and precleaning dischargers. The use of the pretransfer discharger improves transfer efficiency and permits production of copy images of high quality. The precleaning discharger improves cleaning efficiency and ensures satisfactory cleaning of the photosensitive drum. However, the miniaturization of these units has limits. As the space around the photosensitive drum is reduced, therefore, these units are conventionally omitted from the arrangement of the image forming apparatuses. Thus, the quality of copy images produced is low.